1. Field of the Invention
The present invention is directed to a process for destroying insect eggs and larvae in fruit, particularly larvae in commercial fruit intended for shipping from fruit fly infected areas to non-infected areas.
2. Description of the Background
In addition to the obvious advantages of freshness and availability, modern commercial practices of shipping fruit over great distances have provided a new method by which insect infestation can spread. Insect eggs in infested fruit can hatch in locations far removed from the original infestation, endangering commercial fruit and vegetable growing regions in which natural enemies of the pest are absent or few in number. For example, the appearance of the Mediterranean fruit fly in the California fruit growing regions, probably as a result of this process, has required millions of dollars to be spent to maintain pest control.
Current requirements of the U.S. Department of Agriculture are that fruit from an infested area be subjected to a treatment capable of killing 99.9% of eggs and larvae present in fruit before that fruit can be commercially shipped. Until recently, ethylene dibromide (EDB), used as a fumigant, was the method of choice. Recently, EDB has been banned because of concern over possible carcinogenic effects of residues present in fruits. The current method of choice is a hot water bath, with fruit being submerged for 15-20 minutes in water at a temperature of 150.degree. F. (65.degree. C.). However, there are several disadvantages to the hot water bath technique. The first of these is the time of treatment required, which adds significantly to processing time. Additionally, the extended heat treatment may result in a lessening of fruit quality.
Radiation has been proposed as an alternative. Although this should not affect the quality of the fruit and can be carried out in a short time, questions remain both as to the efficacy and the safety of radiation treatment of foods. Additional questions remain relating to the safety of the operators treating the fruit.
A number of techniques exist for processing foods without regard to insect infestation. For example, packaging of fruit by the commercial grower prior to shipment has now become relatively common, as will be appreciated by anyone who has observed the recent increase in pre-package fruits at grocery stores. For example, apples and oranges are often presented in shallow cardboard trays covered with shrinkwrap material (typically 4 or 6 fruits/package). Grapefruit, pineapple, and papaya have been shipped in the United States as individual shrinkwrapped fruit.
However, shrinkwrapping without additional treatment to kill insect larvae has not been practiced in the United States from fruit fly infested areas because of the USDA regulations referenced above. Fruit from infested areas is typically treated by the hot water treatment described above or by some other treatment to kill insect eggs and larvae.
Accordingly, new techniques are needed for treatment of fruit from fruit fly infested areas that ensure 99.9% egg and larvae kill without requiring extensive treatments that adversely affect the quality of the fruit or require long times to accomplish.